Development of an organic EL display as a candidate of next generation display techniques has progressed. Electro-luminescence is shortened to “EL” hereafter. The organic EL display is a self light emitting element and has a structure that is simpler than a liquid crystal display including a white backlight, a liquid crystal substrate (TFT substrate), and a color filter substrate. For this reason, a thin and light flexible display is expected to be produced at low cost in future.
Unfortunately, the organic EL display has the following objectives to be attained.
A. The organic EL display is difficult to achieve high definition.
Currently, in liquid crystal display, displays with a pixel density exceeding 500 ppi have been proposed.
On the other hand, in organic EL display, separate coating is carried out by using a mask vapor deposition method in which a perforated mask having openings is used in order to coat the light emitting layer separately for each RGB, and in the coating process, the pixel density is limited to approximately 350 ppi. In addition, although an inkjet method, a printing method and the like have been proposed, a resolution exceeding 200 ppi is difficult to achieve.
For this reason, in order to obtain a high-definition organic EL display, the “white color conversion scheme” has been proposed in which the emission color is made white and then colorized by being passed through a color filter.
With this scheme, a high definition can be achieved because the light emitting layer is not separately coated. However, the structure comes close to that of the liquid crystal display due to the use of the color filter substrate, and thus, the superiority of the organic EL display as described above cannot be exerted.
B. The light emitting component being a light emitting element exhibits low extraction efficiency.
In the light emitting element, basically, the light emitting component emits uniformly in all directions. Accordingly, a part of the light emitting component emitted in the light emitting layer is totally reflected due to the difference in the refractive indices between the light emitting layer and the air, and is therefore guided only inside the element, not extracted to the outside. For example, when the refractive index of the light emitting layer is 1.8, approximately 20% of the light emitting component is extracted upward and downward, and approximately 80% of the rest is sealed in the light emitting layer. As described above, a known organic EL device has a problem of low light utilization efficiency.
In contrast thereto, in PTL 1, the light extraction efficiency is enhanced by curving the traveling direction of the light emitting component being guided.